Aircraft: BOMBARDIER/CANADAIR UNDIFFERENTIATED OR OTHER MODEL
Phase of flight: Parked
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural MEL / CDL; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor

I was dispatched from my home base of ZZZ to report to ZZZ1 for an aircraft which had smoke in the cabin and flight deck during final approach. I connected through ZZZ3 and did not arrive at the aircraft in question until late that evening. The Flight crew had been put on rest and I was unable to question them about the events that occurred. I met with the on-demand Maintenance Mechanic who was able to talk to the [flight] crew and reviewed what inspection he had completed and what information he had gathered prior to my arrival. He [had] worked the issue while I was en route and was unable to duplicate any such event as was written-up by the flight crew. Due to the serious nature of smoke in an aircraft he and I continued to investigate every source of possible ignition or failure that may cause smoke. I was informed via Maintenance Control that Bombardier requested each pack be run isolated; using APU [bleed] and each engine bleed for a period of 30-minutes on both full 'Hot' and full 'Cold' settings. This lengthy procedure proved to show no hint of smoke developing. Both engines showed no signs of ingestion or leaking of fluid that would cause a poor air quality in the aircraft. I inspected every area of aircraft where electrical connections could possibly create a hazardous situation and found only one suspect area. Upon inspection of the left-hand ceiling lights at Rows One and Two; I discovered lighting fixture had evidence of overheating at the ends of the fixtures. Per MEL 33-21-01A; Category 'C'; I placed the lights on deferral. Per the MEL there is no Maintenance Action required. Due to the manner in which the connecting ends; not the bulb; showed evidence of overheating and the fact that a fire in an aircraft could result in the loss of all souls onboard; I disconnected the [electrical] connectors from either end of the fixture and bagged them to eliminate potential contamination or ignition of the light fixture and connectors. The Lighting Ballast is usually the culprit for these kinds of discrepancies and although I could not detect signs of failure; upon request of Maintenance Control; I also disconnected the ballast on either end and bagged the connectors as well.As a Mechanic; I strive to act in a manner that protects all aircraft I work on and most importantly all those who travel on them. My experience and skill-sets should involve more than just proper workmanship; they should be exemplary; and include all documentation of work performed to protect myself and those who rely on me. I felt I was acting in accordance with the MEL by eliminating the entire system out of an equation where variables could be life threatening. No Maintenance Action was required per the [MEL] book; but per common sense no Maintenance Action was unacceptable. For all future maintenance I shall document any; over and above procedures completed; that are not explicitly called out by the MEL. Log can write-up read backs; and faxed proof reads can go only so far as to getting documentation correct. The responsibility lies in the hands of I; the Mechanic; and I will always remember so. As a Contracted Aircraft Maintainer for Air Carrier X; I am expected to placate all requests made by Air Carrier X's Maintenance Control; but as a Mechanic; it is my duty to question my actions and adhere to procedures set out by the FAA; the Aircraft Manufacturer; and my creed taken as an Aircraft Maintenance Technician (AMT). A Contract Line Mechanic reports that a Regional Jet aircraft had reported smoke in the cabin and flight deck on approach. During troubleshooting of the smoke; he noticed evidence of overheating at the left-hand ceiling ballast fixture and disconnected the electrical connectors at both ends of the fixture; but had failed to include the information when deferring the light assembly.